Traditionally, a reciprocating pump including a plurality of cylinders is used in an oxygen concentrator or the like.
For example, Japanese Patent Laid-open Publication No. 2006-233863 discloses a reciprocating pump including two compressing cylinders disposed to face each other with a motor shaft interposed therebetween. A cylinder head communicating with a cylinder chamber is attached to each of end portions of the two compressing cylinders, and an intake duct through which air is introduced to the cylinder chamber and an exhaust duct through which the compressed air is discharged from the cylinder chamber are connected to the cylinder head. The intake duct and the exhaust duct are pipe fittings separate from the reciprocating pump, and are disposed outside the pump.
In a traditional pump including four cylinders, similarly to the pump of PTL 1, the intake duct and exhaust duct that communicate with the cylinder chamber pump are the pipe fittings separate from the pump, and disposed outside the pump.